C–C Bond-Forming and Bond-Breaking Processes from the Reaction of Diesters with Me₃SnLi. Synthesis of Complex Bridged Polycycles and Dialkyl Aromatic Compounds

Abstract

1,2-Aromatic diesters can be transformed into strained bridged polycyclic structures by a two-step procedure consisting of an initial reductive alkylation promoted by alkaline metals, followed by a reaction of the resulting unsaturated diesters with Me3SnLi. We propose that a stanna-Brook rearrangement plays a fundamental role in the formation of the polycyclic organotin acetals obtained. These unusual compounds could be further functionalized by tin–lithium exchange followed by alkylation of the newly formed tertiary carbanion. Alternatively, dialkylated aromatic hydrocarbons have been prepared via a decarbonilation reaction promoted by Me3SnLi. 1,4-Aromatic diesters were reductively dialkylated and then transformed into norbornadienone derivatives by reaction with Me3SnLi. Several stable dibenzonorbornadienones 41 have been prepared in just two steps starting from anthracene 38. The corresponding naphthalene analogues gave 1,4-dialkylnaphthalenes. The synthetic protocols described provide access to structures that are not easily obtained through existing synthetic methodologies.

Radical Cascade Bicyclization/Aromatization of 1,7‐Enynes with 1,3‐Dicarbonyl Compounds towards 2,3‐Dihydro‐1H‐cyclopenta[a]naphthalenes

“…In 2017, Huang and coworkers found that copper‐catalyzed dehydrogenative formal [3 + 2] cycloadditions of methylnaphthalenes and electron‐deficient alkenes can be used for the construction of 2,3‐dihydro‐1 H ‐cyclopenta[ a ]naphthalenes, which may represent a powerful strategy, although just three examples were given (Scheme 1a) [10] . Shortly after, Paleo, Sardina and coworkers disclosed that dimethyl naphthalene‐1,2‐dicarboxylate could be transformed into 2,3‐dihydro‐1 H ‐cyclopenta[ a ]naphthalene by a two‐step procedure consisting of an initial reductive alkylation of naphthalene diester promoted by alkaline metals, followed by a decarbonilation reaction of the resulting unsaturated diesters with Me 3 SnLi [11] . Alternatively, Lecornué, Thibaudeau and coworkers developed another two‐step process to obtain 2,3‐dihydro‐1 H ‐cyclopenta[ a ]naphthalene by using a Pd‐catalyzed Suzuki−Miyaura coupling reaction and a boron trifluoride etherate‐catalyzed cycloaromatization [12] .…”

“…[10] Shortly after, Paleo, Sardina and coworkers disclosed that dimethyl naphthalene-1,2-dicarboxylate could be transformed into 2,3-dihydro-1H-cyclopenta[a]naphthalene by a two-step procedure consisting of an initial reductive alkylation of naphthalene diester promoted by alkaline metals, followed by a decarbonilation reaction of the resulting unsaturated diesters with Me 3 SnLi. [11] Alternatively, Lecornué, Thibaudeau and coworkers developed another two-step process to obtain 2,3-dihydro-1H-cyclopenta[a]naphthalene by using a Pd-catalyzed Suzuki À Miyaura coupling reaction and a boron trifluoride etherate-catalyzed cycloaromatization. [12] Recently, Chandrasekhar and coworkers reported an elegant work to assemble cyclopentane-fused naphthalenes by using the Lewis-acid-catalyzed intramolecular [4 + 2] cycloaddition/aromatization of alkyne-, allene-, and alkene-tethered aryne insertion adducts (Scheme 1b).…”

Bis-enolates with Extended π-Conjugation Are Powerful Nucleophiles: A Study of Their Alkylation Reactions with Very Hindered C-Electrophiles

“…1 H NMR (500 MHz, CDCl 3 ) δ 7.62 (d, J = 8.0 Hz, 1H), 7.42 (d, J = 1.7 Hz, 1H), 7.28 (dd, J = 8.0, 1.7 Hz, 1H), 5.23 (dhept, J = 12.9, 6.5 Hz, 2H), 2.62 (q, J = 7.1 Hz, 1H), 1.36 (dd, J = 6.3, 4.2 Hz, 12H), 1.25 (d, J = 7.2 Hz, 3H), 0.86 (s, 9H); 13 C{ 1 H} NMR (126 MHz, CDCl 3 ) δ 167.7, 166.9, 148.9, 132. 5 General Procedure B for the Reductive Alkylation of Diisopropyl Phthalate (1) with Secondary Halides: Preparation of Kinetic Isomers 3. A −78 °C suspension of small pieces of sodium (245 mg, 10.6 mmol) and naphthalene (150 mg, 1.17 mmol) in THF (4 mL) was treated with a solution of 1 (250 μL, 1.06 mmol) in THF (1 mL) and stirred for 6 h. The resulting solution was transferred via cannula to a −78 °C flask, washed with THF (5 mL), and treated with a solution of the corresponding secondary halide (1.17 mmol) in DMF (1 mL).…”

“…2 These alkylations occur regioselectively, with the C−C bond formation taking place at both the α positions of the enolate moieties, resulting in two adjacent quaternary centers being formed in the process. Reductive alkylation with different primary bis-electrophiles was achieved starting from anthracene 4 and naphthalene 5 diesters as well to give a variety of fused and bridged polycycles. Although two possible nucleophilic sites are available in these dianionic species, αor γto each enolate group, exclusive α-alkylation was always observed when primary halides or tosylates were used as electrophiles (Scheme 1).…”